Polycarbonate polymers are well known in the art and are advantageous for use in various applications owing to their rigidity and transparency. Similarly, amorphous polyamide resins are also known in the art and are advantageous for use in various applications owing to their rigidity and transparency. In the past, impact modifiers have been added to both polycarbonates and amorphous polyamides in order to improve their impact strength. For example, many rubber polymers are known for use in impact modifying polymers such as polycarbonate and amorphous polyamide. However, many such rubber polymers have low refractive indices, whereby the transparency of the polymers is disadvantageously reduced. For example, the Serini et al U.S. Pat. No. 3,880,783 discloses polycarbonate compositions which include rubber or graft polymers to improve toughness and weld line strength. A polycarbonate having a low refractive index is employed in an attempt to render the compositions transparent. While polychloroprene rubber has a relatively high refractive index of 1.558, chloroprene is not readily copolymerized, whereby its use in graft copolymers is difficult and its compatibility with other polymers is limited. Additionally, rubber-type polysulfides have high refractive indices in the range of 1.6-1.7. However, these rubbers are extremely thermally unstable and therefore are disadvantageous for use in compositions which are thermally processed.
Additional additives have been employed in combination with polycarbonates and amorphous polyamides in order to improve their environmental stress cracking resistance (ESCR). However, improvements in environmental stress cracking resistance in these types of polymers are similarly accompanied by substantial losses in the transparency of the polymers. Accordingly, there is a continuing need to provide transparent polymer compositions with improved properties such as impact strength and/or environmental stress cracking resistance, without sacrificing the transparency of the polymer compositions.